A number of naturally-occurring microorganisms produce polypeptide pesticides, which pesticides are capable of controlling the proliferation of many agricultural pests. For a number of reasons these naturally produced pesticides have not found widespread commercial exploitation, despite their ecological desirableness. In many cases, the organism is difficult to grow, the cost of the pesticide is high, the residual activity of the pesticide in the environment is relatively low, and in individual instances, there are additional drawbacks.
Microorganisms, like most living things, occupy specialized niches in the environment. A rather comprehensive review, entitled "Ecology and Epidemiology of Foliar Bacterial Plant Pathogens," is found in Annual Review of Phytopathology (1983, Hirano, S. S. and Upper, C. D. 21:243-69). Survivability is usually adversely affected when an organism is introduced into an exotic environment. Such is the case with naturally-occurring microorganisms that produce pesticides. In order to be effective as pesticides, the naturally-occurring microorganisms and/or their products must be introduced into exotic environments and, therefore, have insufficient residual activity. However, the potency of the pesticides and their ecological desirableness make them attractive candidates for commercial exploitation, if the detractions to their use could be removed or at least ameliorated.
There is, therefore, substantial interest in finding economical ways to produce these pesticides, to deliver them to the field in a bioactive form, and to enhance and prolong their activity in the environment.
Bulla et al., (1981) J. Biol. Chem. 254:3000-3004, describe the proteinaceous parasporal crystal toxin from B. thuringiensis var. kurstaki. Held et al., (1982) Proc. Natl. Acad. Sci. USA 79:6065-6069, describe the cloning of the gene for proteinaceous parasporal crystal toxin into E. coli and B. subtilis. See also, Schnepf et al. ibid (1981) 78:289-294. Wong et al., (1983) J. Biol. Chem. 258:1960-1967, describe the transcriptional regulatory signals of the B. thuringiensis toxin gene. Klier et al., (1982) EMBO 1:791-799, describe the cloning and expression of a Bt toxin gene. U.S. Pat. No. 4,265,880 describes embedding live insecticidal pathogens in a coacervate microbead.